For more than three decades, mineral water producers in countries like Germany, France and the Netherlands have made murky mineral water clear by adding ozone-enriched air to remove iron particles.

They may have to change their ways as Euro-MPs, fearing the water gets tainted by residual ozone, will attempt to outlaw the method by changing a European Commission proposal in a vote next week in Strasbourg.

“Mineral water is protected by the EU. It is supposed to be a natural drink. If you add ozone it can no longer be called natural mineral water – this is a question of consumer protection,” explained a Parliament official.

Jim Murray, director of the European consumer organisation BEUC agrees: “This treatment leads to a change in the natural bacteria content.

“In our opinion it is a harsh process which does not comply with the concept of ‘natural’,” he added.

But while the Parliament’s plan to ban the use of ozone has won praise from consumer groups, it has been given a decidedly frosty reception by mineral water producers who insist it betrays the assembly’s lack of understanding of the industry.

“This process simply accelerates the separation of iron from the water – it does not change the water. Those MEPs who want it banned simply do not understand the industry. They do not have a mineral water culture. For us this means a step back in time,” said Françoise Buttet, a French producer.

Andreas Rottke, a German mineral water producer, agrees.

He wants the decision to be taken at member-state level. “The German government has no problem with ozone treatment, so I don’t see why the European Parliament has. This is a completely harmless cleaning method which has been used in our country for years.”Given the outcry, the Parliament may try to strike a last-minute deal ahead of next week’s vote.

Parliament sources say the two sides are discussing a compromise which would allow the continued use of ozone, but call for the removal of the term “natural” from “natural mineral water” on the label.

Any change to the Commission’s proposal would have to be approved by EU ministers before becoming law.

They will discuss the amended proposal before sending it back to the Parliament, which shares decision-making powers with the Council in this area, for a second reading.

European Union citizens drank 22 billion litres of mineral water in 1994.